Beyond the five-user assumption: Benefits of increased sample sizes in usability testing

  • Laura FaulknerEmail author


It is widely assumed that 5 participants suffice for usability testing. In this study, 60 users were tested and random sets of 5 or more were sampled from the whole, to demonstrate the risks of using only 5 participants and the benefits of using more. Some of the randomly selected sets of 5 participants found 99% of the problems; other sets found only 55%. With 10 users, the lowest percentage of problems revealed by any one set was increased to 80%, and with 20 users, to 95%.


Usability Test Usability Problem Tick Mark User Deviation Usability Professional 
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Copyright information

© Psychonomic Society, Inc. 2003

Authors and Affiliations

  1. 1.Applied Research LaboratoriesUniversity of Texas at AustinAustin

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